Cyst
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Eulimnadia
clam shrimp
Eulimnadia is a genus of small freshwater branchiopods commonly known as clam shrimp. The genus is notable for its rare androdioecious mating system, where populations consist of males and hermaphrodites but lack pure females. This reproductive strategy has persisted for an estimated 24–180 million years across multiple speciation events, making it one of the most stable examples of androdioecy known in animals. Species are distinguished primarily by the morphology of their resting eggs (cysts), which show distinctive sculpturing patterns. The genus contains approximately 13–25 described species with a cosmopolitan distribution across every continent except Antarctica.